The new leader of the minor opposition People's Party renewed his pledge to strongly keep the ruling bloc in check on Monday, heralding a tough road ahead for President Moon Jae-in seeking its legislative support for his reform agenda.

Co-founder and former presidential candidate Ahn Cheol-soo reclaimed the party's leadership on Sunday, vowing to cement its identity as a "practical, middle-of-the-road" political force and play an active role to keep the government from growing "self-righteous and arrogant."

"While we will cooperate with the government over issues that need our cooperation, we will not neglect our role to keep (the government) in check for our national interests and people's livelihoods," he said during a meeting with senior party members.

"We will criticize with clear principles and alternatives ... The People's Party should stay awake all the time," he added.

His remarks came amid criticism that the party with 40 lawmakers has yet to carve out a solid legislative presence as it has acquiesced in a series of Moon's policy decisions, including a supplementary budget that it initially opposed but later supported.

"Thank you for the opportunity (to lead the party) ... This opportunity is the call to completely reform the party, steel ourselves for a regular parliamentary session and win in the local elections next year," Ahn said.

Ahn's stance put the ruling Democratic Party on edge.

With a regular 100-day parliamentary session set to begin next month, the DP has been seeking the People's Party's backing for a series of legal revisions that Moon has been pushing to retool the tax code and key power organs such as the National Intelligence Service.

The governing party holds only 120 seats in the 299-member legislature, necessitating cooperation from the minor party for the passage of any contested bills.

DP floor leader Woo Won-shik called for Ahn's cooperation, hoping that he would pursue dialogue and compromise rather than confrontation.

"Citizens' expectations are high for Ahn," he said during a party meeting. "I hope he can restore politics that can revive people's livelihoods and yield results through dialogue and compromise rather than causing conflicts and division." (Yonhap)